Manufacture of dialkyl alkanephosphonates



tates No Drawing. Application Septemher 9, 1952 Serial No. 308,726

lilaiil sfpriority, applicationiGreatBritai "Sl mmb r 9 10 Claims. {CL 16091-138) This invention relates a improvements inth'e maufracture of dialkyl alkanephosphonates.

There are already available methods described in the chemical literature for the preparation of dialkyl alkanephosphonates of which the two principal methods are as follows. First, a trialkyl phosphite is reacted with an alkyl halide, preferably the bromide oriodi'de, "in accordance with the well-known Ar'busov reaction which proceeds in accordance with the following equation- Ii -this equation Rand R' indicate alkyl groups and X indicates a halogen atom. In this process whe'reR and .R' are the same it is only necessary to use verysmall quantities of the alkyl halide since, as will be seen from the above Equation 1 the alkyl halide is regenerated.

This method of preparing the dialkyl alkanephosphona-tes, however, suffers from marked disadvantages because, on the one hand, the trialkyl phosphites are compounds which are diflicultly accessible on a commercial .This method is greatly superior to that in Equation No. 1 where dialkyl alkanephosphonates are to be prepared in whichR and R' represent different alkyl groups. This method, however, also has the marked disadvantage that it involves the use of metallic sodium on a large scale in connection with the manufacture of sodium alkoxide or of powdered sodium for the conversion of the dialkyl hydrogen phosphite to the desired dialkyl sodium phosphite and the hazards involved in the use of metallic sodium on a large scale are obvious.

We have now found that we can produce dialkyl alkanephosphonates conveniently by processes which avoid the use of trialkyl phosphites (which are themselves somewhat sensitive to traces of moisture, particularly in the case of trimethyl phosphite) and which also overcome the disadvantage of the use of metallic sodium by the second above-mentioned method.

The present invention is based upon the discovery that a cuprous halide addition compound or complex with a trialkyl phosphite undergoes thermal decomposition, yielding as a reaction product the desired dialkyl alkanephosphonate.

According to the present invention therefore there is formula 2,880,223 Patented J Mar. 31, 1959 ice 2 provided a process lf or the "manufacture of, dialkyl aligneph'osphonates which comprisessubje'eting a cuprous halide addition compound or complex with 'atrialkylphosphite "to thermal decomposition.

The inventionalso provides a process for the manufacture of dialkyl alkanephosphonates which comprises reacting a cuprous halide with a phosphorus t'rihalide and with an alkanol in the'cold and thereafter subjecting the cuprous halide-alkyl phosphite addition compound or complex therebyproduced to thermal decomposition.

The cuprous halide compound which is most convenient is cuprous chloride and "the phosphorus trihalide which is "most convenient is' phosphorus trichloride.

The decomposition of the cuprous halide addition compound or complex which ma he represented by the decomposition in this way, however, produces yields a which are somewhat low, which may be iln the neighbourhood of 20% A feature of .the invention therefore consists in that the thermal decomposition of the cuprous halidjealkyl phosphite addition compound or complex is elfected by heating the, said additioncompound or complex in suspension in a medium whichis an inert and stable liquid at the temperature of the thermal decomposition. The reaction may, for example, be carried out in a high boiling solvent such as diphenyl or diphenyl ether.

It will be appreciated that the present invention is not confined to the .PrQ uction of dialkyl alkan'ephosp'honates in which all of the talk-y} groups are identical but includes the case where the cuproufs halide and phos- "phorus trihalide are reactedtogether with a :mixture of aliphatic alcohols.

In our copending application, S.;N. 308.72 7, we have disclosed the production of other'compounds by decomposition of this complex.

The following example will serve toillust'rate'the manner in which the present inventioil ma'y 'be carried into effect.

Example solid product (CH O) P.CuCl was filtered 01f, washed with dry petrol (200 ml.) and dried in a vacuum' desiccator. The yield was of the theoretical amount.

A portion of the white solid thus prepared was rapidly suspended in diphenyl ether and the mixture heated with stirring to 200 C. When decomposition was complete the dimethyl methanephosphonate was distilled out from the diphenyl ether under vacuum (12 mm.). The yield was approximately 70% of the theoretical amount.

We claim:

1. A process of preparing -a complex of the formula (RO) P.CuX wherein R is a lower aliphatic hydrocarbon group and X is selected from the class consisting of chlorine, bromine and iodine which comprises forming a mixture consisting essentially of at least one lower unsubstituted alkanol, a cuprous halide and an inert solvent, and adding phosphorus trichloride to said mixture at a temperature of the order of -5 C. while agitating said mixture.

2; A 'pro'cess 'br' isrefisiiag '(CH O) P.CuCl whic'hcomprises forming a mixture conagitating said mixture.

a complex of the formula sisting essentially of methanol, cuprous chloride and an inert solvent and adding phosphorus. trichloride to said mixture at a temperature of the order of 5 C. while 3. A process 'of preparing a lower unsubstituted dialkyl alkanephosphonate which comprises suspending in a high fboiling liquid a complex of the formula (RO) P.CuCl, wherein R represents an unsubstituted lower alkyl group,

heating said suspension to a temperature of substantially 200, C. at a pressure of the order of, but not below, normal atmospheric pressure, said liquid being one which is inert and stable. at. said .temperature'and pressure.

4. A method as defined in cla'im3 wherein said liquid is selected from the group consisting of diphenylether and diphenyl. 7 1 j e r 5. A method of preparing a lower dialkyl alkanephosphonate which comprises reacting a lower unsubstituted alkanol with cuprouswchloride-and phosphorus trichloride to form the complex (KO) P.CuCl, where R is a lower unsubstituted alkylgroup, and then suspendingsaid complex in a high boiling liquid and heatingthe'resulting suspension at a temperature of substantially 200 C. and a pressure of the order of, but not below, normal atmospheric pressure to thereby decompose said complex and produce said lower dialkyl methanephosphonate, said liquid being one which is inert and-stable at said temperature and pressure.

6. A method of producing a lower dialkyl alkanephosphonate which comprises forming a mixtureco'nsisting essentially of at least one unsubstituted lower alkanol,

cuprous chloride and an inert solvent, adding phosphorus 7. A process as defined in claim 6 wherein said high boiling'liquid is selected from the group consistingof d p e yl n iphcny ltsi't Davis 'et"al.:

8. A process of producing dimethyl methanephosphonate which comprises forming a mixture of methanol, cuprous chloride, and an inert solvent, adding phosphorus trichloride to said mixture at a temperature of the order of --5 C. while stirring said mixture, thereby forming a complex of the formula (CH O) P.CuCl, suspending said'complex in a'high-boiling liquid and decomposing said complex by heating the suspension thus formed at a temperature of substantially 200 C. and a pressure of the order of, but not less than, ordinary atmospheric pressure, said high boilingliquid being one which'is inert and stable at said temperature and pressure.

9. A process as defined in claim 8 wherein said high boiling liquid. is selected from the group consisting of :liphenyl diphenylether..

10. A process of preparing dimethyl methanephosphonate which comprisesislowly adding phosphorus trichloride to a mixture of'cuprous chloride and methanol in toluene with stirringata temperature of substantially 5 C., thereby forming the complex (CH O) P.CuCl, removing said omple x from said toluene,- suspending said complex in. diphenylether, decomposing said com- .plex by heating the suspension thus formed substantially to 200 C. with stirring, at atmospheric pressure thereby forming dimethyl methanephosphonate,

Referenees Citedfin the file of this patent UNITED STATES PATENTS -Woodstoek Nov. 22, 1938, OTHER REFERENCES ArbusOff: Berichte der Deu. Chen 1., vol. 38 (1905),

35 I Lindet: Annales de Chemie et de Physique 6, 11, pp.

Beilstein: Band I (Bis 1 Jan. 1910), p. 285, line 16 -J. Am. Chem. Soc. 58, 2151-2153 'Arbuzov et al.: Chem. Abstracts, vol. 29 (1935), p.

2146. (Abstract of Jour. Gen. Chem. USSR, vol. 4 

1. A PROCESS OF PREPARING A COMPLEX OF THE FORMULA (RO)3P.CUX WHERIN R IS A LOWER ALPHATIC HYDROCARBON GROUP AND X IS SELECTED FROM THE CLASS CONSISTING OF CHLORINE, BROMINE AND IODINE WHICH COMPRISES FORMING A MIXTURE CONSISTING ESSENTIALLY OF AT LEAST ONE LOWER UNSUBSTITUDE ALKANOL, A CUPROUS HALIDE AND AN INERT SOLVENT, AND ADDING PHOSPHOROUS TRICHLORIDE TO SAID MIXTURE AT A TEMPERATURE OF THE ORDER OF -5*C. WHILE AGITATING SAID MIXTURE
 3. A PROCESS OF PREPARING A LOWER UNSUBSTITUTED DIALKYL ALKANEPHOSPHONATE WHICH COMPRISES USPENDING IN A HIGH BOILING LIQUID A COMPLEX OF THE FORMULA (RO)3P.CUCL, WHEREIN R REPRESENTS AN UNSUBSTITUTED LOWER ALKYL GROUP, HEATING SAID SUSPENSION TO A TEMPERATURE OF SUBSTANTIALLY 200*C. AT A PRESSURE OF THE ORDER OF, BUT NOT BELOW, NORMAL ATMOSPHERIC PRESSURE, SAID LIQUID BEING ONE WHICH IS INERT AND STABLE AT SAID TEMPERATURE AND PRESSURE.
 5. A METHOD OF PREPEARING A LOWER DIALKYL ALKANEPHOSPHONATE WHICH COMPRISES REACTING A LOWER UNSUBSTITUTED ALKANOL WITH CUPROUS CHLORIDE AND PHOSPHOROUS TRICHLORIDE TO FORM THE COMPLEX (RO)3P.CUCL, WHERE R IS A LOWER UNSUBSTITUTED ALKYL GROUP, AND THEN SUSPENDING SAID COMPLEX IN A HIGH BOILING LIQUID AND HEATING THE RESULTING SUSPENSION AT A TEMPERATURE OF SUBSTANTIALLY 200*C. AND A PRESSURE OF THE ORDER OF, BUT NOT BELOW, NORMAL ATMOSPHERIC PRESSURE TO THEREBY DECOMPOSED SAID COMPLEX AND PRODUCE SAID LOWER DIALKYL METHANEPHOSPHONATE, SAID LIQUID BEING ONE WHICH IS INERT AND STABLE AT AID TEMPER 